Variation of horizontal stiffness of laminated rubber bearings using new boundary conditions

Abstract

Base isolation is today an accepted design philosophy for earthquake resistant design of structural system and sensitive instruments. Among the different types of base isolation bearings, laminated elastomeric isolation bearing is one of the most attractive devices. The elastomeric rubber bearings should be protected from failure or instability because the instability of rubber bearings may result in serious damage to superstructure. Predicting of behavior of laminated rubber bearings usually are obtained from Haringx’s theory and have been developed by many researchers and they have proposed nonlinear mechanical model for multilayer elastomeric bearings. However, in the past theoretical and experimental studies, the effects of rotation in the bottom and top ends of elastomeric isolation bearing have been neglected. In this study, an analytical method are presented and formulated by consideration of rotation of top plate and bottom plate of multilayer rubber bearing as new boundary conditions. According to these rotations, horizontal stiffness of laminated rubber bearing which is the one of the most important characteristics of bearings will change. Comparisons of theoretical and experimental results show that the present analysis model has good accuracy for analyzing laminated rubber bearings. Examples are presented to demonstrate the validity of the develop method in predicting the horizontal stiffness of laminated elastomeric bearings with different geometric parameters. The results of this study have been shown that the horizontal stiffness of laminated rubber bearing will increase or decrease according different boundary conditions.